Nonwoven havng a corrugated structure, intermediate product, and method for producing a nonwoven having a corrugated structure

ABSTRACT

The invention relates to a three-dimensional structured nonwoven, which is formed from staple fibers (F 1 , F 2 , F 3 ). In order to be able to produce such a nonwoven using simple means, the invention proposes providing groove channels (R) on at least one of its surfaces (O), which channels are milled into the surface (O) provided with the groove channels.

The invention relates to a three-dimensional structured nonwoven composed of staple fibers, and to an intermediate product and to a method for producing such a nonwoven. Three-dimensional nonwoven fabrics having a corrugated structure are known, which are usually produced using one of the following three methods:

-   1) Structo method. Here, a nonwoven fabric is set upright in     corrugated shape by means of rolls similar to gear wheels. This is     done so as to create heavy nonwovens for mattresses or cushions, and     is also referred to as vertical laying. The laid nonwoven fabric has     a multiple of the m²-weight of the starting nonwoven fabric. -   2) Embossing method. Here, the nonwoven is generally placed into a     heated mold and solidifies in the mold as it cools. In this method,     the material is compacted at certain locations and becomes hard. No     material savings occur. -   3) Joining of two components. Here, one of the components has a very     much greater shrinkage capacity than the other. The shrinking     process is triggered by heating, for example, and a non-uniform     structure occurs.

A method is known from U.S. Pat. No. 5,223,319, in which a stack of fibers supplied in strip shape is conveyed through a working gap formed between two rolls that rotate in opposite directions. In this connection, the one roll is equipped with radially projecting spikes on its circumferential surface, while the other roll is provided with correspondingly shaped and arranged depressions on its circumferential surface. The rotation of the rolls is synchronized in such a manner that the spikes of the one roll engage into the depressions of the other roll. In this way, the stack of fibers passed through the working gap is compacted there and, at the same time, provided with dome-shaped recesses arranged at regular intervals, each of which recesses has a passage opening at its highest point. The nonwoven obtained in this manner is not consolidated further, but rather can be used directly for absorption of oil or the like.

A method in which a stack of fibers supplied in strip shape, in the non-consolidated state, is provided with a corrugated structure and subsequently consolidated, is known from DE 19 57 727 A (=U.S. Pat. No. 3,616,159). In this method, the stack of fibers is also passed through a working gap between two rolls that rotate in opposite directions, wherein here, the rolls are configured in the manner of gear wheels, the teeth of which mesh with one another in the working gap. In this manner, the fiber strip is compacted in the working gap and is given a corrugated structure, in which the depressions formed on its top and bottom side extend transverse to the longitudinal expanse of the nonwoven obtained. For consolidation, a binder is applied to the nonwoven after the corrugated structure is removed from the mold.

A method comparable to the state of the art according to DE 19 57 727 A is known from EP 0 810 078 A1. There, too, a consolidated nonwoven is obtained, which has a corrugated structure having groove channels that extend transverse to the longitudinal direction of the nonwoven.

Against the background of the state of the art as explained above, the task has arisen of making available a three-dimensionally structured nonwoven that can be produced using simple means.

Likewise, an intermediate product was to be indicated, which allows the production of such a nonwoven.

Finally, a method for simplified production of a three-dimensionally structured nonwoven was to be indicated.

With reference to the nonwoven, the invention has accomplished this task in that such a nonwoven has at least the characteristics indicated in claim 1.

An intermediate product suitable for the production of a nonwoven according to the invention is indicated in claim 10.

A [word missing: nonwoven] according to the invention can be produced by means of using a method that comprises at least the work steps indicated in claim 11, according to the invention.

Advantageous embodiments of the invention are indicated in the dependent claims and will be explained in detail below.

The invention relates to a nonwoven fabric that already has a corrugated structure before a consolidation process. Greater absorption capacity for moisture and particles can be produced by means of the grooves.

Because the nonwoven is not compacted, fewer fibers are required for formation of the nonwoven. Natural fibers can also be used for forming such a structured nonwoven.

The structured nonwoven can be consolidated in a subsequent step. In this regard, consolidation preferably takes place in a manner different from air suction.

Formation of the nonwoven is suitable for staple fibers having a gauge of 0.7-70 dtex and for staple lengths from 10 mm. Production is extremely simple.

A three-dimensional structured nonwoven according to the invention, composed of staple fibers, is characterized in that groove channels exist on at least one of its surfaces, which channels are milled into the surface provided with the groove channels.

It is therefore typical for a nonwoven according to the invention that the groove channels provided according to the invention are not produced by means of the displacement of fibers and accompanying compaction of the fibers in the sections of the nonwoven that border on the groove channels, but rather in that according to the invention, the groove channels are formed by means of the removal of fibers. In other words, in a finished nonwoven according to the invention, there are fewer fibers, on average, in the thickness section in which the groove channels are formed than in the thickness region in which no groove channels are present.

In this regard, nonwovens according to the invention are characterized in that the fibers are preponderantly oriented parallel to the groove channels in the region of the nonwoven that borders directly on the groove channels. This parallel orientation occurs when the groove channels are milled into the fiber stack that has not yet been consolidated. In this regard, the milling tool engages into the surface to be provided with the groove channels, in each instance, so that the fibers gripped by it are pulled out of the surface, forming the groove in question. Concomitantly, the fibers that lie bordering on the fibers in question but remain in the nonwoven, which fibers form the lateral delimitation surfaces of the groove channels in the finished nonwoven according to the invention, are oriented in the direction of the relative movement of the milling tool and fiber stack. A typical characteristic of nonwovens according to the invention, and, accordingly, also of an intermediate product according to the invention, is therefore the orientation of a greater number of fibers present close to the corresponding groove in a direction oriented parallel to its longitudinal expanse, in other words along the progression of the corresponding groove channel.

In contrast, the fibers of the fiber stack that remain below the groove channels remain essentially unaffected by the milling process so that a nonwoven according to the invention typically has a different fiber orientation below the groove channels than in the region of the lateral delimitation surfaces of the groove channels. Thus, the fibers of a nonwoven according to the invention can be present in random orientation, for example, below the groove channels.

Three-dimensionally structured nonwovens according to the invention, composed of staple fibers, in which nonwovens at least ten groove channels are formed per nonwoven width, are particularly suitable for practical use.

In this regard, nonwovens according to the invention, the groove channels of which have a maximum depth of 5 mm, can not only be produced particularly well, but rather are also characterized by optimized use properties.

From a production-technology point of view, it proves to be particularly advantageous if the groove channels run parallel to one another. In this regard, in the present text “parallel” should not be understood in the strict geometric sense, in each instance, but rather in the sense of a person skilled in the art of textile technology. In other words, for example, it means that even those embodiments in which the groove channels do not run precisely parallel represent advantageous embodiments of the invention, as long as the groove channels have a basically rectilinear orientation, in which they are aligned next to one another.

In the case of a parallel orientation of the groove channels in this sense, a fiber stack can be guided in a linear movement along a milling tool to produce the nonwoven, which tool simultaneously mills two or more of the groove channels that run parallel to one another into the corresponding surface of the nonwoven.

If specific patterns or spatial expanses are required of the groove channels, then the groove channels can also be configured to be non-continuous, i.e. interrupted. For example, they can extend over only a partial length of the corresponding nonwoven according to the invention. This can be brought about, for example, in that the milling tool is lowered into the surface of the fiber stack only at a certain section, and then moved over the corresponding length relative to the surface until the groove channel has attained the intended length, and the milling tool is raised off the fiber stack again.

A particularly simple way of production, which can be carried out particularly effectively, occurs if, in the case of a three-dimensionally structured nonwoven according to the invention, composed of staple fibers, the groove channels are configured to be continuous over the length of the nonwoven. This embodiment makes it possible, for example, to move a fiber stack, which has been made available in the manner of a strip, continuously along the respective milling tool.

The progression of the groove channels can be determined by means of the shape of the milling tool. For example, nonwovens according to the invention can be produced by using a correspondingly shaped milling tool, in which nonwovens the groove channels have a corrugated progression. Such a progression can be produced, for example, by using a milling tool configured as a roll, in which wave-shaped projections that run around the roll are provided on the circumferential surface of the roll.

In accordance with the above explanations, an intermediate product that is present in the non-consolidated state, for the production of a nonwoven configured according to the invention, is characterized, according to the invention, in that the intermediate product is formed by a stack of fibers in which groove channels are milled into at least one surface. A method according to the invention, for producing a nonwoven configured according to one of the above explanations, accordingly comprises the following working steps:

-   -   a) making available a fiber stack composed of fibers,     -   b) milling groove channels into one of the surfaces of the fiber         stack,     -   c) consolidating the fiber stack provided with the groove         channels to produce the nonwoven.

The fiber stack made available in working step a) can be produced in any conventional manner. For example, the airlay method is suitable, in which the fibers are laid to form a fiber stack using an aerodynamic method, for example by means of an air flow, in which stack they are then arranged in random orientation, for example (see https://de.wikipedia.org/wiki/nonwoven fabric).

It is understood, as has already been mentioned several times above, that the fiber stack made available according to the invention can also be present as a strip that is processed in the manner according to the invention in continuous throughput.

In this regard, it has turned out [words missing: to be advantageous], in particular also with regard to geometrically precise formation of the groove channels produced according to the invention, if the length of the fibers amounts to at least 10 mm.

For milling the groove channels into the non-consolidated fiber stack in working step b), a roll that rotates about an axis of rotation can be provided, which roll is provided with a fitting. This fitting engages into the surface of the fiber stack to be worked during milling, and tears the fibers that have gotten into its engagement region out of the surface. For this purpose, the fitting can be present in the form of a fitting set or can consist of pins, hooks or disks.

For example, the fiber stack can be held on a screen surface with a partial vacuum for milling the groove channels. This partial vacuum does not lead to permanent compacting of the fiber stack, so that after the partial vacuum is eliminated, the fiber stack relaxes again and is present in a density that is essentially equal to its original density.

The fiber stack, held in suitable manner, for example in the manner explained above, by means of the application of a partial vacuum, is moved along a rotating roll, on the circumferential surface of which an annular structure is formed by means of suitably shaped projections. The projections of the rotating roll that come into engagement with the surface to be worked then throw fibers out of the nonwoven, which fibers are suctioned away and can be passed to the process of fiber stack formation in a stage of the production process that precedes the process of fiber stack formation.

A particularly simple way of procedure occurs when the groove channels are milled into the fiber stack in a material running direction. This particularly holds true when the fiber stack is present as a fiber strip, which is continuously guided along the milling tool. In this regard, the material running direction typically corresponds to the longitudinal direction of the fiber stack. Groove channels that extend in the material running direction of the fiber stack can be produced in particularly simple manner using a roll-shaped milling tool, the axis of rotation of which is oriented transverse to the material running direction of the fiber stack.

Consolidation of the nonwoven, which follows milling of the groove channels, can take place in any known manner. However, consolidation with support by means of air suction should be avoided, since undesirable compaction of the nonwoven would occur as a result. Optimally, consolidation is carried out in such a manner that the density of the nonwoven after consolidation is essentially equal to the density before consolidation, in other words insignificant compaction of the nonwoven, at most, occurs during the course of consolidation.

Thus, in working step c), consolidation of the fiber stack to produce the nonwoven can take place by means of the application of an adhesive that glues the fibers to one another. Alternatively or in addition, in working step c) consolidation of the fiber stack to produce the nonwoven can also take place by means of the application of heat, so that fibers that lie against one another melt, at least partially, in the region of their contact zone, and a material-fit connection between the fibers occurs, due to the material of the fibers melting into one another. Methods known from the state of the art, which allow consolidating a nonwoven without air suction and accompanying compaction, are: hydrogen consolidation, adhesive application, foam application, calendering, hot-air treatment, melting of binding fibers, needling, fulling, microwave heating, infrared heating, spray application of adhesives, ultrasound bonding.

In the following, the invention will be explained using an exemplary embodiment.

FIG. 1 shows a nonwoven in cross-section, in the production (running) direction.

FIG. 2 shows a detail of the nonwoven according to FIG. 1 in a top view.

The nonwoven V has groove channels R, which have been milled into the nonwoven V with a depth t. In FIG. 1, the fiber cross-sections of fibers F1, F2 are indicated with dots, the fibers being oriented parallel to the groove channels R, since groove milling occurred in the material running direction ML.

Below the milling depth t, the nonwoven V has any desired structure. Thus, the fibers F3 can form a random-orientation nonwoven or a multi-layer paneled nonwoven.

The groove channels R are produced using a rapidly rotating roll, not shown here, which is provided with a fitting. The fitting can consist of a fitting set, pins, hooks or disks.

For the production of the nonwoven V, a strip-shaped fiber stack produced in conventional manner, for example by means of the airlay method, is made available as an intermediate product; the fibers F1, F2, F3 are present in random orientation in this product.

Due to the milling processing of the surface O of the nonwoven V to be provided with the groove channels R, the fibers that are situated in the region of the groove channels R to be produced are torn out of the surface of the fiber stack by the fitting of the rotating roll. At the same time, due to the relative movement between the fibers F1, F2, F3 that remain in the fiber stack, the fitting of the tool and/or the fibers that have been torn out, the fibers F1, F2, which laterally delimit the corresponding groove channel R, are brought into an orientation parallel to the straight-line progression of the groove channels R. In contrast, the fibers F3 that are present in the thickness regions of the nonwoven V that lie deeper relative to the surface O remain in their original random orientation, so that fibers F3 are present in random orientation also below the groove channels R.

After milling of the groove channels R, the nonwoven V can be consolidated by using one of the methods already mentioned above, which are known for this purpose from the state of the art.

A nonwoven V according to the invention is therefore characterized in that it has groove channels R so as to have a three-dimensional structure. The groove channels R are milled. The fibers F1, F2 that delimit the groove channels R laterally are oriented parallel to the progression of the respective groove channels R.

Accordingly, the invention relates to a three-dimensional structured nonwoven V, which is formed from staple fibers F1, F2, F3. So as to be able to produce such a nonwoven V using simple means and with a minimized need for fibers F1, F2, F3 required for production, the invention proposes providing groove channels R on at least one of the surfaces O of the fiber stack, which grooves are milled into the surface O.

REFERENCE SYMBOLS

-   F1, F2 fibers in orientation parallel to the groove channels R -   F3 fibers in random orientation -   ML material running direction -   O surface of the nonwoven V -   R groove channels -   T depth of the groove channels [Translator's Note: In the text the     lower case letter t was used.] -   V nonwoven 

1. A three-dimensional structured nonwoven (V) composed of staple fibers (F1, F2, F3), characterized in that groove channels (R) exist on at least one of its surfaces (0), which channels are milled into the surface (0) provided with the groove channels (R).
 2. The three-dimensional structured nonwoven (V) according to claim 1, characterized in that in a region of the nonwoven (V) that borders directly on the groove channels (R), the fibers (F1, F2) are preponderantly oriented parallel to the groove channels (R).
 3. The three-dimensional structured nonwoven (V) according to claim 2, characterized in that the fibers (F1, F2) oriented preponderantly parallel to the groove channels (R) are present in a region that delimits the groove channels (R) laterally.
 4. The three-dimensional structured nonwoven (V) according to claim 2 or 3, characterized in that the nonwoven (V) has a different orientation of the fibers (F3) below the groove channels (R).
 5. The three-dimensional structured nonwoven (V) according to claim 4, characterized in that the nonwoven (V) has a random orientation of the fibers (F3) below the groove channels (R).
 6. The three-dimensional structured nonwoven (V) according to one of the preceding claims, characterized in that at least 10 groove channels (R) are formed per nonwoven width.
 7. The three-dimensional structured nonwoven (V) according to one of the preceding claims, characterized in that the groove channels (R) have a maximum depth of 5 mm.
 8. The three-dimensional structured nonwoven (V) according to one of the preceding claims, characterized in that the groove channels (R) run parallel to one another.
 9. The three-dimensional structured nonwoven (V) according to one of the preceding claims, characterized in that the groove channels (R) are configured to be continuous over the length of the nonwoven (V).
 10. The three-dimensional structured nonwoven (V) according to one of the preceding claims, characterized in that the groove channels (R) have a corrugated progression.
 11. An intermediate product for the production of a nonwoven (V) structured according to one of the preceding claims, wherein the intermediate product is present in the non-consolidated state, characterized in that the intermediate product is formed by a stack of fibers (F1, F2, F3), into at least one surface of which groove channels (R) are milled.
 12. A method for producing a nonwoven (V) configured according to one of the above claims, comprising the following work steps: a) making available a fiber stack composed of fibers (F1, F2, F3), b) milling groove channels (R) into a surface (0) of the fiber stack, c) consolidating the fiber stack provided with the groove channels (R) to produce the nonwoven (V).
 13. The method according to claim 12, characterized in that the length of the fibers (F1, F2, F3) amounts to at least 10 mm.
 14. The method according to one of claim 12 or 13, characterized in that the fibers (F1, F2, F3) have a gauge of 0.7-70 dtex.
 15. The method according to one of claims 12 to 14, characterized in that in working step b), the groove channels (R) are milled by means of a rotating roll that is provided with a fitting.
 16. The method according to claim 15, characterized in that the fitting consists of a fitting set, of pins, of hooks or of disks.
 17. The method according to one of claims 12 to 16, characterized in that in working step c), consolidation of the fiber stack to produce the nonwoven (V) takes place by means of application of an adhesive that glues the fibers (F1, F2, F3) to one another.
 18. The method according to one of claims 12 to 17, characterized in that in working step c), consolidation of the fiber stack to produce the nonwoven takes place by means of application of heat, so that fibers (F1, F2, F3) that lie against one another melt, at least partially, in the region of their contact zone, and a material-fit connection occurs between the fibers (F1, F2, F3), due to the material of the fibers (F1, F2, F3) melting into one another. 